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Anthropogenic litter (AL), or trash, in urban rivers is abundant, mobile, and shows a wide diversity of types (e.g., plastic, metal, textiles) and input pathways. Previous work suggests AL can be moved along with naturally occurring organic matter (e.g., sediment, leaf litter, and wood) according to particle properties and stream hydrology. Debris dams are key sites of organic matter retention in streams. AL likely accumulates in debris dams; however, measurements of AL dynamics in debris dams and non-debris dam habitats in urban streams are uncommon, as are measurements of AL composition within different zones of debris dam structure. We measured AL density as count (no./m2) and mass (g/m2) in paired debris dam and non-debris dam sites in urban streams in Baltimore, Maryland, USA and Chicago, Illinois, USA. Within debris dams, we recorded AL by 4 zones: 1) overhanging, 2) floating, 3) submerged, and 4) riparian. As expected, there was more AL within debris dams compared with non-debris dam habitats. Across all sites, most AL was composed of plastic materials, but we also noted distinctions in composition. Heavy items, such as ceramic materials, dominated non-debris dam sites, whereas expanded polystyrene and cigarette litter were more common in debris dams. Similarly, there was evidence of AL sorting within debris dams, with distinct composition between the floating (lightweight items) and submerged zones (heavy materials). AL composition in the riparian and overhanging zones showed no differences to one another or to the floating or submerged zones. Overall, AL had patchy distribution in streams and followed well-known processes that drive particle transport. Because debris dams are hot spots of biological activity, accumulation of AL within debris dams may facilitate interaction with stream biota. Improved understanding of the spatial distribution of AL within urban streams is valuable to improve models of AL density and movement at the watershed scale and to inform policies to prevent or remove AL from polluted sites. [ABSTRACT FROM AUTHOR]

Accumulation of plastic litter in aquatic environments negatively impacts ecosystems and human livelihood. Urban areas are assumed to be the main source of plastic pollution in these environments because of high anthropogenic activity. Yet, the drivers of plastic emissions, abundance, and retention within these systems and subsequent transport to river systems are poorly understood. In this study, we demonstrate that urban water systems function as major contributors to river plastic pollution, and explore the potential driving factors contributing to the transport dynamics. Monthly visual counting of floating litter at six outlets of the Amsterdam water system results in an estimated 2.7 million items entering the closely connected IJ river annually, ranking it among the most polluting systems measured in the Netherlands and Europe. Subsequent analyses of environmental drivers (including rainfall, sunlight, wind speed, and tidal regimes) and litter flux showed very weak and insignificant correlations (r = - 0.19–0.16), implying additional investigation of potential drivers is required. High-frequency observations at various locations within the urban water system and advanced monitoring using novel technologies could be explored to harmonize and automate monitoring. Once litter type and abundance are well-defined with a clear origin, communication of the results with local communities and stakeholders could help co-develop solutions and stimulate behavioral change geared to reduce plastic pollution in urban environments. [ABSTRACT FROM AUTHOR]

Despite the substantial impact of rivers on the global marine litter problem, riverine litter has been accorded inadequate consideration. Therefore, our objective was to detect riverine litter by utilizing middle-scale multispectral satellite images and machine learning (ML), with the Tisza River (Hungary) as a study area. The Very High Resolution (VHR) images obtained from the Google Earth database were employed to recognize some riverine litter spots (a blend of anthropogenic and natural substances). These litter spots served as the basis for training and validating five supervised machine-learning algorithms based on Sentinel-2 images [Artificial Neural Network (ANN), Support Vector Classifier (SVC), Random Forest (RF), Naïve Bays (NB) and Decision Tree (DT)]. To evaluate the generalization capability of the developed models, they were tested on larger unseen data under varying hydrological conditions and with different litter sizes. Besides the best-performing model was used to investigate the spatio-temporal variations of riverine litter in the Middel Tisza. According to the results, almost all the developed models showed favorable metrics based on the validation dataset (e.g., F1-score; SVC: 0.94, ANN: 0.93, RF: 0.91, DT: 0.90, and NB: 0.83); however, during the testing process, they showed medium (e.g., F1-score; RF:0.69, SVC: 0.62; ANN: 0.62) to poor performance (e.g., F1-score; NB: 0.48; DT: 0.45). The capability of all models to detect litter was bounded to the pixel size of the Sentinel-2 images. Based on the spatio-temporal investigation, hydraulic structures (e.g., Kisköre Dam) are the greatest litter accumulation spots. Although the highest transport rate of litter occurs during floods, the largest litter spot area upstream of the Kisköre Dam was observed at low stages in summer. This study represents a preliminary step in the automatic detection of riverine litter; therefore, additional research incorporating a larger dataset with more representative small litter spots, as well as finer spatial resolution images is necessary. [ABSTRACT FROM AUTHOR]

Macrolitter, especially macroplastics, (> 0.5 cm) negatively impact freshwater ecosystems, where they can be retained along lake shores, riverbanks, floodplains or bed sediments. Long-term and large-scale assessments of macrolitter on riverbanks and lake shores provide an understanding of litter abundance, composition, and origin in freshwater systems. Combining macrolitter quantification with hydrometeorological variables allows further study of leakage, transport, and accumulation characteristics. Several studies have explored the role of hydrometeorological factors in influencing macrolitter distribution and found that river discharge, runoff, and wind only partially explains its distribution. Other factors, such as land-use features, have not yet been thoroughly investigated. In this study, we provide a country-scale assessment of land-use influence on macrolitter abundance in freshwater systems. We analyzed the composition of the most commonly found macrolitter items (referred to as 'top items', n = 42,565) sampled across lake shores and riverbanks in Switzerland between April 2020 and May 2021. We explored the relationship between eleven land-use features and macrolitter abundance at survey locations (n = 143). The land-use features included buildings, city centers, public infrastructure, recreational areas, forests, marshlands, vineyards, orchards, other land, and rivers and canals. The majority of top items are significantly and positively correlated with land-use features related to urban coverage, notably roads and buildings. Over 60% of top items were found to be correlated with either roads or buildings. Notably, tobacco, food and beverage-related products, as well as packaging and sanitary products, showed strong associations with these urban land-use features. Other types of items, however, did not exhibit a relationship with land-use features, such as industry and construction-related items. Ultimately, this highlights the need to combine measures at the local and regional/national scales for effective litter reduction. [Display omitted] • 60% of macrolitter items at freshwater shores correlate with roads or buildings. • Industry and construction items show insignificant correlations with local land use. • Results suggest combining local and regional/national litter reduction measures. [ABSTRACT FROM AUTHOR]

The presence of plastic debris along shorelines is a widespread problem, and plastic debris can interact directly with marine wildlife. In northeast Brazil, the Antillean manatees are the most common marine mammals and use estuarine waters mainly as their home range. We aimed to investigate the characteristics of plastic debris on the estuarine-oceanic continuum and the accumulation density of plastic on beaches. The density of plastic debris on beaches located in transitional areas was 7–10-fold greater than that on beaches in estuarine and oceanic areas. Fragments were considered the most abundant form of plastic debris on all the beaches. Our findings could lead to improved pollution management in this marine protected area, principally due to the risks of remobilizing small plastic particles through tides and wind effects that scatter them in resting and feeding manatees areas. • Fragments were the most abundant form of plastic debris in the beaches. • The most common color of the plastics was white. • Macro- and mesoplastics were found widely present on all the beaches. • Sand spits provided a barrier to the transport of plastic debris. [ABSTRACT FROM AUTHOR]

This work describes for the first time the presence of pyroplastics in the Canary Islands (Spain). A total of 300 pyroplastics, identified between 2021 and 2024 in three beaches of the island of Tenerife, present mainly grey and dark colors, a mean weight of 6.8 ± 13.4 g and mean dimensions of 34.2 ± 17.0 mm (X), 24.5 ± 12.2 mm (Y) and 14.4 ± 6.4 (Z). A wide variety of encapsulated and semi-encapsulated materials were also found in the pyroplastics matrix, such as rocks, wood, charcoal and unmelted plastic inclusions. Fourier-transform infrared spectroscopy analysis revealed that polyethylene and polypropylene were the main types of plastic found, 61.3 % and 33.6 %, respectively. However, an important number of pyroplastics composed of more than one polymer were also found, coexisting even mixtures of polyester and polyethylene or polyethylene and styrene-ethylene-butylene-styrene in the same matrix. X-ray fluorescence spectroscopy analysis revealed the presence of a wide range of elements, being remarkable the high concentration of some heavy metals such as Pb and Cr, registering mean concentration values of 205.3 ± 6.3 mg·kg−1 and 51.1 ± 8.9 mg·kg−1, respectively. A good correlation was also found for these two metals in a total of 22 pyroplastics, which could be indicative of the presence of PbCrO 4 as additive, widely used in the plastic industry for its bright yellow color, but currently regulated and restricted due to its harmful effects on human and environment health. Also noteworthy is the large variety of remains of marine organisms identified attached to the surface of the pyroplastics, such as algae, bryozoans, arthropods and molluscs, among others, which could indicate that these formations may act as a transport vector for such marine organisms. [Display omitted] • Pyroplastic pollution (n = 300) was first reported on the Canary Islands (Spain). • An important number of pyroplastics composed of more than one polymer were found. • Pyroplastics contained encapsulated and semi-encapsulated materials. • A positive correlation between Pb and Cr concentrations was found. • Pyroplastics are acting as a substrate of different marine organisms. [ABSTRACT FROM AUTHOR]

Literature review identified seven principal pathways of plastic debris entry into river systems: waste water treatment plants; combined sewer overflows; on-site wastewater treatment systems; road and rail transport systems; agriculture; industrial sources; and diffuse litter. A further category of 'microplastics' reflects their multiple potential sources, including microplastic breakdown within rivers. Regulatory and management bodies necessarily make operational decisions based on resource limitations and significant uncertainty due to sparse or missing data, requiring a substantial degree of inference. To support this need, we develop a rapid, desk-based approach based on risk criteria to 'fingerprint' likely pathways of plastic pollution based on catchment characteristics. Characteristics of the River Wye system in the UK are reviewed identifying a risk-based 'fingerprint' of potential pathways of plastic entry or accumulation of plastic debris, represented graphically as a colour-coded 'traffic lights' classification. This 'fingerprinting' approach is based on desk-based inference from published materials as a rapid and resource-efficient alternative to intensive data collection, supporting prioritization of further investigation or response measures. We recommend replication of this 'fingerprinting' approach in other river catchments to support operational management of plastic pollution. Where feasible, it may also be down-scaled where sub-catchment or major river reach properties differ significantly. HIGHLIGHTS Unique catchment characteristics influence likely sources of plastics in rivers Seven potential plastic sources were identified, with a residual microplastics category Literature, interviews and surveys can rapidly 'fingerprint' likely plastic sources Fingerprinting can prioritize management and investigations in specific catchments [ABSTRACT FROM AUTHOR]

This study aims to present the identification, abundance, and chemical characterization of plastics in the intertidal zone sediment of two selected beaches in Kota Kinabalu city, Sabah, Malaysia. Plastic debris was classified according to weight and size and was identified for its heavy metal concentrations and polymer types. Results showed that a higher abundance, by more than 2-fold, of plastic debris was found in Kebagu beach (28.7 g) compared to ODEC, UMS (13.4 g). FTIR analysis showed that polypropylene (PP) and polyethylene (PE) were the dominant plastic polymers on both beaches, followed by polystyrene (PS) and polyethylene terephthalate (PET). Five heavy metals (arsenic, chromium, copper, zinc, and nickel) were detected from four types of plastics. The results showed that the concentration of Zn was higher in all four types of plastics on both beaches, with a range of 41 mg/kg–135.3 mg/kg, followed by Cr and As, while Ni was the lowest concentration detected in PE on both beaches: 5.6 mg/kg (ODEC) and 5.1 mg/kg (Kebagu stations). This study confirmed the presence of macro-, meso- and microplastics in both stations. Further studies remain necessary for a better understanding of the sources and fates of the pollutant in the marine environment. Findings from the studies of the Kota Kinabalu beaches have provided baseline data and a clearer understanding of the distribution of plastic debris. This demonstrates that commitments and actions are required to mitigate the potential risk to the ecological system and human health. [ABSTRACT FROM AUTHOR]

Land-based plastic waste, carried to the sea through rivers, is considered a main source of marine plastic pollution. However, most plastics that leak into the environment never make it into the ocean. Only a small fraction of plastics that are found in the terrestrial and aquatic compartments of river systems are emitted, and the vast majority can be retained for years, decades, and potentially centuries. In this perspective paper we introduce the concept of river systems as plastic reservoirs. Under normal conditions, hydrometeorological variables (such as wind, runoff and river discharge) mobilize, transport and deposit plastics within different river compartments (e.g., riverbanks, floodplains, lakes, estuaries). The emptying of these plastic reservoirs primarily occurs under extreme hydrological conditions (e.g., storms, floods). In this paper we specifically focus on the retention mechanisms within different river compartments, and their effect on the fate of the plastics that are accumulated on various timescales. We aim to introduce the concept of rivers as (long-term) sinks for plastic pollution, and provide suggestions for future research directions.

Large-scale monitoring of anthropogenic marine litter in the Barents Sea was carried out in 2012–2018. The marine litter composition was estimated by recording by-catch from pelagic and bottom trawling. Litter on the sea surface (floating litter) was also taken into account during visual observations. The contents of 949 pelagic and 1477 bottom trawls were analyzed. Marine litter was recorded in 256 pelagic and 571 bottom trawl catches and in 454 cases during visual observations. Litter was sorted into plastic, wood, metal, rubber, textiles, paper, and glass. The occurrence of plastic prevailed in all litter records. It covered 71% of marine litter observed on the surface, 97% in pelagic trawls, and 78% in bottom trawls. Fishery litter prevailed in plastic litter (about 65% of its weight). Wood was recorded in 19% of surface litter observations, 1% in pelagic trawls and 13% in bottom ones. Metal, rubber, paper, textiles, and glass were occasionally observed; however, their weight (except glass) could be very large. Thus, metal and wood prevailed by weight on the bottom (45 and 36.8%, respectively). Wood prevailed in pelagic layers, being 73% of the total litter weight. The volume of plastic and wood prevailed on the sea surface (50 and 47%, respectively). The average density of all types of litter on the sea bottom was about 7.9 kg/km2. Some significant differences in the litter composition were recorded between the southwestern and northeastern areas of the Barents Sea. [ABSTRACT FROM AUTHOR]

The Eastern Tropical and South-Eastern Pacific region is of global biodiversity importance. At COP26, the governments of Costa Rica, Panama, Colombia, and Ecuador committed to the expansion of existing MPAs to create a new Mega MPA, safeguarding the Eastern Tropical Pacific Marine Corridor. It offers a profound step forward in conservation efforts but is not specifically designed to protect against the more diffuse anthropogenic threats, such as plastic pollution. We combine published data with our own unpublished records to assess the abundance and distribution of plastic pollution in the region. Macro- and microplastic concentrations varied markedly and were not significantly different when comparing areas inside and outside existing MPA boundaries. These findings highlight the diffuse and complex nature of plastic pollution and its ubiquitous presence across MPA boundaries. Understanding the sources and drivers of plastic pollution in the region is key to developing effective solutions. • Analysis of 430 sites to assess plastic pollution in ET/SE Pacific. • No significant difference in plastic levels inside/outside of Marine Protected Areas. • New Mega MPA will not protect against ingress by plastic pollution. • Imperative to clearly establish sources and drivers of plastic pollution in region. [ABSTRACT FROM AUTHOR]

Plastic pollution is ubiquitous in aquatic environments worldwide. Rivers connect terrestrial and marine ecosystems, playing a key role in the transport of land-based plastic waste towards the sea. Emerging research suggests that in estuaries and tidal rivers, tidal dynamics play a significant role in plastic transport and retention dynamics. To date, observations in these systems have been limited, and plastic transport dynamics during single tidal cycles remain poorly understood. Here, we investigated plastic transport, trapping, and re-mobilization of macroplastics (> 0.5 cm) in the Saigon River, focusing on short-term dynamics of individual tidal cycles. We used GPS trackers, released at different stages of the tidal cycle (ebb, flood, neap, spring). Plastic items demonstrated dynamic and intermittent transport behavior. Items spent almost half of the time (49%) temporarily stopped, mainly due to their entrapment in vegetation, infrastructure, or deposition on riverbanks. Items were almost always re-mobilized within 10 h (85%), leading to successive phases of stopping and transport. Tidal dynamics also resulted in bidirectional transport of plastic items, with median daily total transport distance within the 40 km study reach (8.9 km day−1) over four times larger than the median daily net distance (2.0 km day−1). The median retention time of plastic items within the reach was 21 days (mean = 202 days). In total, 81% of the retrieved items were trapped within water hyacinths, emphasizing the important role of floating vegetation on river plastic transport dynamics. With this paper, we aim to provide data-driven insights into macroplastic transport and retention dynamics in a tropical tidal river. These are crucial in the design of effective intervention and monitoring strategies, and estimating net plastic emission from rivers into the sea. [Display omitted] • Tracked floating macro-plastic items in the Saigon River spent nearly half of their time in the system stopped. • Trajectories show a succession of transport, stopping, and re-mobilization phases. • Tidal dynamics lead to bidirectional transport and large differences between total and net transport velocities. • 80% of the retrieved items were entrapped by in-stream floating vegetation. • Impact of hydrological variability and plastic properties should be further explored. [ABSTRACT FROM AUTHOR]

Despite recent advances in remote sensing of large accumulations of floating plastic debris, mainly in coastal regions, the quantification of individual macroplastic objects (>50 cm) remains challenging. Here, we have trained an object-detection algorithm by selecting and labeling footage of floating plastic debris recorded offshore with GPS-enabled action cameras aboard vessels of opportunity. Macroplastic numerical concentrations are estimated by combining the object detection solution with bulk processing of the optical data. Our results are consistent with macroplastic densities predicted by global plastic dispersal models, and reveal first insights into how camera recorded offshore macroplastic densities compare to micro- and mesoplastic concentrations collected with neuston trawls.

Plastics in rivers and lakes have direct local impact, and may also reach the world's oceans. Monitoring river plastic pollution is therefore key to quantify, understand and reduce plastics in all aquatic ecosystems. The lack of harmonization between ongoing monitoring efforts compromises the direct comparison and combination of available data. The United Nations Environment Programme (UNEP) launched guidelines on freshwater plastic monitoring, to provide a starting point for practitioners and scientists towards harmonized data collection, analysis, and reporting. We developed a five-step workflow to support to design effective plastic monitoring strategies. The workflow was applied to three rivers (Rhine, Mekong and Odaw) across relevant gradients, including geography, hydrology, and plastic pollution levels. We show that despite the simplicity of the selected methods and the limited duration of the data collection, our harmonized approach provides crucial insights in the state of plastic pollution in very different river basins globally. [Display omitted] • Monitoring river plastic pollution is key to quantify, understand, and reduce plastics in all aquatic ecosystems • We developed a five-step workflow to develop harmonized river plastic monitoring strategies based on the UNEP guidelines • Application to the Rhine (Europe), Odaw (Africa) and Mekong (Asia) provided harmonized plastic pollution estimates [ABSTRACT FROM AUTHOR]

Abstract Composition, spatial distribution and temporal evolution of marine litter on the Spanish Mediterranean seafloor were assessed. The data derive from Spanish MEDITS surveys over 11 years and were analysed by GIS. A total amount of 2197.8 kg of litter was collected. Marine litter (by weight) was composed of plastics (29.3%), clinker (28.4%), wood (10.2%), metal (9.7%) and glass (6.2%). Its density varied among Areas (Alboran Sea > Valenciana >Alboran Island > Tramontana). For the last 11 years, the marine litter has remained stable or decreases in some case. The information provided by this study is a useful baseline to study such debris on the Spanish seafloor. The MEDITS survey has proven to be an appropriate monitoring tool, also of use to assess future control measures. Highlights • A total amount of 2197.8 kg of marine litter was collected from the study area. • Composition: Plastics: 29.3; Clinker: 28.4; Wood: 10.2; Metal: 9.7; Glass: 6.2. • Marine litter density varied along the Spanish Mediterranean Coast. • For the last 11 years, marine litter remained stable or decreases in some case • MEDITS is a useful tool to assess reduction measures of marine litter [ABSTRACT FROM AUTHOR]

Excessive mismanaged debris along tropical coasts pose a threat to vulnerable mangrove ecosystems. Here, we examined the spatial, seasonal and environmental drivers of anthropogenic debris abundance and its potential ecological impact in peri-urban mangroves across Hong Kong. Seasonal surveys were conducted in both landward and seaward zones, with identification, along belt transects, of macrodebris (>5 mm) based on material type and use. Our results indicate spatial variability in debris abundance and distribution, with plastic being the predominant material type identified. Both plastic and non-plastic domestic items covered the most surface area. Debris aggregation was highest at the landward zones, consistent with the literature. In the dry season, more debris accumulated and covered greater surface area in both seaward and landward zones. These results confirm that land-derived debris from mismanaged waste, rather than debris coming from the Pearl River, is the primary source of anthropogenic debris pollution threatening Hong Kong's mangroves. [Display omitted] • Plastic is the most common debris found in peri-urban mangroves. • Landward zones of mangroves have higher concentrations of debris. • Abundance and coverage of debris increases in the dry season in mangrove forests. • Wind speed is a viable predictor of debris abundance. • Mismanaged waste, not the Pearl River, is Hong Kong mangroves' main pollution source. [ABSTRACT FROM AUTHOR]

Rivers function as a pathway for plastic pollution to enter the marine environment. This study presents one of the first field estimates of macroplastic emissions from the Mahiga Creek into its estuary. Thirty-minute plastic counting surveys were conducted for 31 days with the use of videos and a collecting trawl. The captured plastics were classified according to the OSPAR marine litter manual. The three main categories were crisp packets (27.96 %), small bags (27.08 %), and plastic/polystyrene pieces (2.5–50 cm) (18.35 %). Intraday and daily changes in plastic flux values were compared. Plastic flux comparisons between holidays and regular days were also done. No relationship between plastic flux and discharge was found on days without rainfall (r = 0.0237). However, a significant increase in plastic flux was observed during rainfall events. The findings in this study present an insight into different factors that may affect macroplastic emissions in the Philippines. • Visual observations were used to estimate the emissions of a Philippines river. • The three most found items were crisp packets, small bag, and pieces (2.5–50 cm). • No plastic flux discharge relationship was observed on days without rainfall. • Visual counts were done during the Sinulog Festival and Lunar New Year. • The median hourly emission in this study was 468 items/h (352–604 items/h). [ABSTRACT FROM AUTHOR]

It was thought that the Southern Ocean was relatively free of microplastic contamination; however, recent studies and citizen science projects in the Southern Ocean have reported microplastics in deep-sea sediments and surface waters. Here we reviewed available information on microplastics (including macroplastics as a source of microplastics) in the Southern Ocean. We estimated primary microplastic concentrations from personal care products and laundry, and identified potential sources and routes of transmission into the region. Estimates showed the levels of microplastic pollution released into the region from ships and scientific research stations were likely to be negligible at the scale of the Southern Ocean, but may be significant on a local scale. This was demonstrated by the detection of the first microplastics in shallow benthic sediments close to a number of research stations on King George Island. Furthermore, our predictions of primary microplastic concentrations from local sources were five orders of magnitude lower than levels reported in published sampling surveys (assuming an even dispersal at the ocean surface). Sea surface transfer from lower latitudes may contribute, at an as yet unknown level, to Southern Ocean plastic concentrations. Acknowledging the lack of data describing microplastic origins, concentrations, distribution and impacts in the Southern Ocean, we highlight the urgent need for research, and call for routine, standardised monitoring in the Antarctic marine system. [ABSTRACT FROM AUTHOR]

Through a literature survey and meta-data analysis, monitoring methods and contamination levels of marine micro- and macroplastics in seawater were compared between the North Pacific and the world's other ocean basins. The minimum cut-off size in sampling and/or analysis of microplastics was crucial to the comparison of monitoring data. The North Pacific was most actively monitored for microplastics and showed comparatively high levels in the global context, while the Mediterranean Sea was most frequently monitored for macroplastics. Of the 65 extracted mean abundances of microplastics in seawater from the North Pacific, two (3.1%) exceeded the lowest predicted no-effect concentration (PNEC) proposed thus far. However, in the context of business-as-usual conditions, the PNEC exceedance probability may be expected to reach 27.7% in the North Pacific in 2100. The abundance of marine plastics in seawater, which reflects the current pollution status and marine organisms' waterborne exposure levels, is a useful indicator for marine plastic pollution. For regional and global assessments of pollution status across space and time, as well as assessment of ecological risk, two microplastic monitoring approaches are recommended along with their key aspects. Although microplastic pollution is closely linked with macroplastics, the monitoring data available for floating macroplastics and more extent to mesoplastics in most ocean basins are limited. A more specific framework for visual macroplastic survey (e.g. fixed minimum cut-off size, along with survey transect width and length according to survey vessel class) is required to facilitate data comparison. With the implementation of standardised methods, increased efforts are required to gather monitoring data for microplastics and—more importantly—floating macroplastics in seawater worldwide. [Display omitted] • Sampling methods and abundance levels of plastics in seawater were reviewed. • Microplastic abundances decreased according to increasing minimum cutoff size. • Marginal seas including coasts were more polluted with microplastics than open ocean. • Macroplastic data were limited and geographically biased in the North Pacific. • The future microplastics in seawater of the North Pacific will well exceed the PNECs. Capsule: Seawater plastic monitoring methods and contamination levels in the North Pacific and other ocean basins were reviewed. [ABSTRACT FROM AUTHOR]

Possible access routes of macro and mesoplastics, acting as the main sources of pollution in the coastal ecosystem, are examined as a case study on four beaches along the Istanbul coast. A total number of 3787 items belonging to 12 categories of debris types were collected as follows: macroplastics 47.8%; mesoplastics 9.2%; and others 43.0% such as paper pieces, glass pieces and metal beverage cans. Clean-coast and carbonyl indexes were also used to identify the level of cleanliness of the sampling sites. The clean-coast index revealed that all of the sample sites were categorized as extremely dirty. Moreover, carbonyl index results indicate that 35.7% of the samples were at a high oxidation level indicating that some of the particles relatively spend more time on beaches. The litter concentration and surface oxidation results were addressing issues that should be taken into consideration to improve litter management strategies of the beaches. [Display omitted] • Macro/mesoplastics are dominant pollutants in Istanbul coastal ecosystems. • The complex problem of pollutant by plastics needs coordinated solution and ecological restoration. • Clean-coast and carbonyl indexes were used for the first time for İstanbul coastal area. • Control of plastic materials may be possible with consistent recycling policies. [ABSTRACT FROM AUTHOR]

[Display omitted] • Linking observed entanglement prevalence to plastic debris exposure in SSD-approach. • Quantifying a spatially-explicit indicator of potential entanglement impacts. • Presenting application options for life cycle and risk assessments. Marine animals have been known to interact with and become entangled in plastic debris for decades. Despite increasing annual input volumes of plastic waste to the natural environment and the threat this constitutes to marine biodiversity, impacts of mismanaged plastic waste generally remain unquantified in environmental impact assessments. In this paper, we develop a Species Sensitivity Distribution (SSD) approach for estimating a spatially differentiated indicator of potential macroplastic entanglement impacts with global coverage of the world's oceans. This constitutes a key modelling step that contributes towards the inclusion of plastic litter effects in impact assessments. We gathered entanglement incidence data for 20 species of marine mammals, turtles and birds from different populations and marine regions. To capture species-specific sensitivities to entanglement and spatially varying concentrations of plastic debris, concentration–response modelling of field data was used to develop the SSD-based model. This was achieved by linking population specific entanglement records to corresponding regional areas of exposure and an existing global model of plastic debris concentrations. The SSD was further applied to derive an estimate of the Potentially Affected Fraction (PAF) of species on a global scale, highlighting regional hotspots of potential entanglement impacts at current levels of marine plastic pollution. This indicator can be adapted and applied in impact assessments in order to account for potential impacts of mismanaged plastic waste ending up in marine ecosystems. [ABSTRACT FROM AUTHOR]

Plastic in the environment is considered an emerging pollutant of global concern. In spite of intensive research, many questions remain open, such as the processes that drive the deposition and remobilization of plastic debris on river beaches. The objectives of this study were: i) to analyze the influence of the natural hydrological fluctuations and wind intensity on the distribution of mesoplastic (0.5–2.5 cm) and macroplastic (>2.5 cm) debris in beach sediments of a large river, ii) to describe the type of plastic debris found and iii) to explore potential relations between the number of items and weight of macro- and mesoplastics. Our results suggest that, during lowering water levels, flow removes the plastic debris and transports it further downstream. Conversely, when the beach sediments remain exposed during long periods, the plastic debris accumulates considerably. Nevertheless, the influence of wind intensity on plastic debris transport was comparatively negligible. In other words, in our study the water flow had a greater capacity to remobilize and transport plastic debris than the wind. The most abundant mesoplastic items were foam, hard plastic, film and small fragments of fishing line. The dominant macroplastic items recorded were pieces of fishing line (nylon) and cigarette filters (cellulose acetate), typically discarded by beach users. Other items found in large quantities were soft packaging elements (expanded polystyrene), hard plastic containers (polystyrene, polyethylene terephthalate) and beverage bottles (polyethylene terephthalate), typical items of domestic use in the Paraná River region. Finally, we found that the density of macroplastic items is highly correlated to the density of mesoplastic items, serving as surrogate for further estimations. Our results could help to develop better mitigation strategies in seasonal riverscapes, based on the influence of the hydrological cycle and the characteristics of the most abundant meso- and macroplastics. [Display omitted] • Hydrology plays a crucial role in the dynamics of plastic debris on river beaches. • The influence of wind intensity on plastic debris dynamics was minor. • Plastic debris tend to accumulate on river beaches during long periods of sediment exposition. • The dominant macroplastics were fishing lines, cigarette butts, packaging and bottles. • The density of macroplastic items can be used as surrogate for density of mesoplastic. [ABSTRACT FROM AUTHOR]

Despite recent advances in remote sensing of large accumulations of floating plastic debris, mainly in coastal regions, the quantification of individual macroplastic objects (>50 cm) remains challenging. Here, we have trained an object-detection algorithm by selecting and labeling footage of floating plastic debris recorded offshore with GPS-enabled action cameras aboard vessels of opportunity. Macroplastic numerical concentrations are estimated by combining the object detection solution with bulk processing of the optical data. Our results are consistent with macroplastic densities predicted by global plastic dispersal models, and reveal first insights into how camera recorded offshore macroplastic densities compare to micro- and mesoplastic concentrations collected with neuston trawls. [ABSTRACT FROM AUTHOR]

Marine plastic litter pollution has become an emerging threat to the Philippines, especially in Palawan. This study was conducted to investigate the macroplastic litter and determine the clean-coast index (CCI) of the residential and non-residential sites on the coasts of Puerto Princesa, Palawan. Plastic litters were sampled from 21 coastal barangays by delineating a 50-m-long transect line with three 4 m × 4 m quadrats. The litter sampled were counted and sorted into categories. The results showed that 17 sites were contaminated with plastic litters. In terms of residential and non-residential sites, the east coast has thrice as much plastic, 2.61 items/m2 and 1.26 items/m2 compared to west coast with only 1.57 items/m2 and 0.14 items/m2, respectively. The plastics sampled were predominantly fishing line (nylon), food packaging, and fragments. The calculated CCI revealed that 76% of the sites sampled were categorized as dirty and extremely dirty. [Display omitted] • First study on marine plastic litter in Palawan, Philippines • Sites on the east coast have three times more plastics than the west coast. • Collected plastics were mostly fishing line nylon, food packaging and plastic fragments. • Seventy six percent of the sites can be categorized as dirty and extremely dirty. [ABSTRACT FROM AUTHOR]

We present reflectance measurements collected from virgin and ocean-harvested plastics. Virgin plastics included high and low density polyethylene (HDPE, LDPE), polypropylene (PP) as well as polystyrene (PS). Ocean-harvested plastics were ropes, sheets, foam, pellets and fragmented items previously trawled from the North Pacific Garbage Patch. Nadir viewing angles and plastic pixel coverage were varied to advance our understanding of how reflectance shape and magnitude can be influenced by these parameters. We also investigated the effect of apparent colour of plastics on the measured reflectance from the ultraviolet (UV - 350 nm), visible, near to shortwave infrared (NIR, SWIR - 2500 nm). Statistical analyses indicated that the spectral reflectance of the plastics was significantly correlated to the percentage pixel coverage. There was no clear relationship between the reflectance observed and the viewing nadir angle but dampened materials seemed to be more isotropic (near-Lambertian) than their dry counterparts. A loss in reflectance was also determined between dry and wet plastics. Location of absorption features was not affected by the apparent colour of objects. In general, ocean-harvested plastics shared more identical absorption features (~960, 1215, 1440, 1732, 1920 nm) and had lower reflectance intensity compared to the virgin plastics (~980 nm). Prospects for satellite retrieval of plastic type and pixel plastic coverage are discussed based on Top-of-Atmosphere (TOA) signal simulated through radiative transfer computation using the documented plastic reflectances. Non-linear relationships between TOA reflectance and plastic coverage were observed depending on wavelength and plastic type. Most of the plastics analysed impact significantly the TOA signal but two plastic types did not produce strong signal at TOA (hard fragments, LDPE). Nevertheless, all plastic types produced detectable signals when observations were simulated within the sunglint direction. The measurements collected in this study are an extension to available high quality spectral reference libraries and can support further research in developing remote sensing algorithms for marine litter. ga1 • Showcase remote sensing as complementary plastic litter monitoring strategy. • Present hyperspectral measurements of virgin and ocean plastics from UV to SWIR. • Explore anisotropic reflectance properties of plastics at varying pixel coverages. • Show the apparent colour of plastics affects UV to SWIR spectral shape and magnitude. • Assess satellite remote sensing of plastics using radiative transfer solutions. [ABSTRACT FROM AUTHOR]

Marine litter affects various habitats across the world. This review focuses on the Adriatic region, considering the presence of marine litter as well as microplastics (mPs) and macroplastics (MPs) in different environments (water, beach, seabed and biota). Data from 53 scientific papers were critically analysed, providing a snapshot of this type of contamination, and evidencing critical issues. The final part of the review provides considerations on spatial and temporal trends, comparing data with the available information provided by transport forecasting models. It emerges that the most investigated areas are those most subjected to the contribution of rivers, tourism or have the greatest relevance to nature conservation. Our analysis also reveals that, even though many international research projects have played a fundamental role in the creation of shared methods and protocols, currently available data are difficult to compare. Nevertheless, our results enhance knowledge of the state of the art in the research carried out so far, and on the situation regarding pollution due to the marine litter in the Adriatic Sea, as well as highlighting avenues for future investigation. Image 1 • The studies on the presence of marine litter in the Adriatic region are collected. • Plastic has been found in sea water, sea bed, beaches and biota. • Polyolefin is the main type of plastic found in the investigated environments. • Comparison and monitoring data is difficult when uniform protocols are not adopted. • The available protocols should be improved to obtain more representative data. All the main studies on the presence of marine litter in the Adriatic region are analysed, finding that different protocols were used, and highlighting the different types of plastic present in seawater, sea bed, beaches and biota. [ABSTRACT FROM AUTHOR]

Studies on macroplastic pollution in freshwater systems are rare compared to the marine environment. Nevertheless, freshwater systems are worthy to be equally investigated as they are pathways of plastic to the ocean and lakes may act as (temporary) sinks. The aim of this study was to identify sources for plastics and influences on its distribution in a limnic environment. Anthropogenic litter (>5 mm) was monitored semi-annually over a three-year period at four sandy bank border segments of Lake Tollense in Mecklenburg-Western Pomerania, Germany. The selected beaches represent different expositions and vary in their level of anthropogenic activity. Considering all six samplings, mean abundance of anthropogenic litter is 0.2 ± 0.1 items/m2 or 130.9 ± 91.0 items/100 m beach length. The averaged mass of anthropogenic litter is 0.5 ± 1.0 g/m2 or rather 218.7 ± 284.6 g/100 m. Plastic consistently is the predominate material (72%) and cigarette butts are the most found items. A higher pollution by anthropogenic litter is found at the end of tourist season unveiling the impact of anthropogenic activity on litter abundance. Additionally, litter transport via tributaries into the lake plays a role. Testing the detection of anthropogenic litter via aerial images taken by unmanned aerial vehicles resulted in good recovery rates when minimizing the flight height. Furthermore, the analysis of anthropogenic litter distribution displayed on the images showed litter accumulation areas at the border of sandy beach areas. The deployment of marine guidelines in a freshwater environment did work well, however, small changes in the protocol are suggested for future lake beach studies dealing with anthropogenic litter pollution. Image 1 • All studied lake beaches are polluted by anthropogenic litter. • Plastic was the dominant material (72%). • Tributaries and anthropogenic activities influence litter abundances. • Differences in litter abundance were significant between seasons. • Unmanned aerial vehicle images were successfully used for plastic detection. [ABSTRACT FROM AUTHOR]

Research into the scope of litter pollution in freshwater systems has shown similar levels to the marine and coastal environment. Global model estimates of riverine emission rates of anthropogenic litter are largely based on microplastic studies as long-term and holistic observations of riverine macroplastics are still scarce. This study therefore aims to contribute a detailed assessment of macrolitter in the transitional waters of three major North Sea tributaries: Ems, Weser, and Elbe. Litter surveys were carried out in four river compartments: along the embankment, on the river surface, in the water column, and on the river bed. The data revealed spatio-temporal variability and distinct pollution levels for each compartment. Beaches had the highest debris diversity and were significantly more littered than vegetated sites and harbors. Stony embankments were least polluted. Benthic litter levels appeared substantial despite rapid burial of objects being likely due to high suspended sediment loads. Two extrapolation approaches were tested to scale daily and annual litter emission quantities of surface- and subsurface-floating litter. Using the mean (median) litter item mass from water column samples, total annual mass discharges were calculated: ∼0.9 (0.2) t y−1 to ∼2.8 (0.5) t y−1 emitted via the Ems, ∼1.3 (0.2) t y−1 to ∼12.0 (1.9) t y−1 through the Weser, and ∼14.7 (2.4) t y−1 to ∼801 (128) t y−1 carried into the North Sea by the Elbe. These rates deviate considerably from previous model estimates of plastic loads discharged by these three rivers. Future studies should therefore ground-truth model estimates with more river-specific and long-term field observations. Overall, the estimated plastic debris discharge quantities account for <1% of the total mass of mismanaged plastic waste per catchment. Image 1 • Anthropogenic debris was holistically surveyed in the lower Ems, Weser, and Elbe. • Amounts varied between embankment type, river surface, water column, and river bed. • Observations generally confirmed larger rivers to have higher pollution levels. • Field-based litter outflow rates diverged from past model-based estimates. • Future studies should ground-truth model estimates with more field observations. [ABSTRACT FROM AUTHOR]

Plastic debris presents a serious hazard to marine ecosystems worldwide. In this study, we developed a method to evaluate high-resolution maps of plastic emissions from the land into the sea offshore of Japan without using mismanaged plastic waste. Plastics were divided into microplastics (MicPs) and macroplastics (MacPs), and correlations between the observed MicP concentrations in rivers and basin characteristics, such as the urban area ratio and population density, were used to evaluate nationwide MicP concentration maps. A simple water balance analysis was used to calculate the annual outflow for each 1 km mesh to obtain the final MicP emissions, and the MacP input was evaluated based on the MicP emissions and the ratio of MacP/MicP obtained according to previous studies. Concentration data revealed that the MicP concentrations and basin characteristics were significantly and positively correlated. Water balance analyses demonstrated that our methods performed well for evaluating the annual flow rate, while reducing the computational load. The total plastic input (MicP + MacP) was widely distributed from 210–4776 t/yr and a map showed that plastic emissions were high for densely populated and highly urbanized areas in the Tokyo metropolitan area, as well as other large urban areas, especially Nagoya and Osaka. These results provide important insights that may be used to develop countermeasures against plastic pollution and the methods employed herein can also be used to evaluate plastic emissions in other regions. [ABSTRACT FROM AUTHOR]

Plastic pollution in aquatic ecosystems is an emerging environmental risk, as it may negatively impacts ecology, endangers aquatic species, and causes economic damage. Rivers are known to play a crucial role in transporting land‐based plastic waste to the world's oceans, but riverine ecosystems are also directly affected by plastic pollution. To better quantify global plastic pollution transport and to effectively reduce sources and risks, a thorough understanding of origin, transport, fate, and effects of riverine plastic debris is crucial. In this overview paper, we discuss the current scientific state on plastic debris in rivers and evaluate existing knowledge gaps. We present a brief background of plastics, polymer types typically found in rivers, and the risk posed to aquatic ecosystems. Additionally, we elaborate on the origin and fate of riverine plastics, including processes and factors influencing plastic debris transport and its spatiotemporal variation. We present an overview of monitoring and modeling efforts to characterize riverine plastic transport, and give examples of typical values from around the world. Finally, we present an outlook to riverine plastic research. With this paper, we aim to present an inclusive and comprehensive overview of riverine plastic debris research to date and suggest multiple ways forward for future research. This article is categorized under: Science of Water > Water QualityWater and Life > Stresses and Pressures on Ecosystems [ABSTRACT FROM AUTHOR]

Plastic pollution is one of the most acute environmental topics of our time. While there is a great scientific effort to tackle this problem, it has not always been well-coordinated or properly targeted. In this short review, we call for scientists to get involved in three crucial topics (threats) underestimated—or ignored—in freshwater systems: (i) plastic-species entanglement, (ii) plastic as nesting material, and (iii) macroplastic debris coming from mismanaged household solid waste. Reducing the knowledge gaps between marine and freshwater environments will be crucial to solute the plastic pollution problem effectively and globally. Therefore, we make a plea here to reinforce research activities on these three issues in freshwater environments worldwide. [ABSTRACT FROM AUTHOR]